Free electronic circuit design and schematic diagram
In high fidelity (hi-fi) audio system, the harmonic distortion level is kept as low as possible. To make sure that the amplifier handle the sigal perfectly, the response of many hi-fi audio systems is designed beyond the audio range, include the handling capability to process infrasonic (below 20Hz) and ultrasonic (higher than 20kHz) signals. Although this capability is useful to […]
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Notch filter is known as band-cut filter or band-reject filter. The fuction of this filter is to remove some frequency portion of a signal. The schematic diagram of this filter circuit, a second order notch filter is depicted in the figure below. The formula is actually complicated, but by taking the R3=R4 and C1=C2, the filter’s frequency response formula become […]
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The function of this circuit is similar with the hum filter in our previous circuit, but it use transistors instead of op-amps. It uses BC109 transistors, but any low noise high gain type will be suitable. This hum filter is adjustable via trimmer pots to fine tune it’s notch depth. The figure below shows the schematic diagram of the […]
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The simple low-pass filter is shown in Figure below. The filter has a 20dB/decade roll-off after its corner frequency fc. Its low-pass frequency gain (f->0) is defined by R3/R1. This allows low-frequency gains other than unity to be obtained. R2 should be chosen equal to the parallel combination of R1 and R3 to minimize error due to bias current. LMV721/722 […]
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For high pass filter, this circuit is similar to low-pass filter circuit, but the position for resistors and capacitor are interchanged. Here is the circuit’s schematic and formula: Similar with low pass design guide, the resistor and capacitor should be chosen according to the formula, and the resistor value should be: Much higher than equivalent leakage resistance of the capacitor. […]
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A second order filters can be constructed using LC (inductor-capacitor) passive circuits, and they have been implemented for radio frequency for cheap and simplicity. For audio frequency range, unfortunately the size for the inductor and capacitor become too large, space consuming, and the most important is they’re really expensive. Because of this, active filter is commonly used for audio application. […]
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It is fun to make a variable space in your small room, but it’s hard to make the actuator to move your wall or room partition. Using analog audio line delay, you can adjust your room virtually. Just turn a knob in your audio set and you can adjust your room size. The circuit described here will make your dream […]
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